Since phosphor screens are very efficient devices for converting electrical energy to light, these screens are found in an increasing number of devices covering a wide range of applications. Conversion may be direct as in electro luminescent panels or by intermediate radiation processes such ultraviolet ray production in flourescent lights, x-ray production in diagnostic devices or cathode rays in television picture tubes and image intensifiers. Depending upon the application, other properties than efficiency must be considered in choosing a method for fabrication of a particular screen. When cathode ray images are to be focussed on the screen such properties as uniformity, average thickness, texture, color, contrast, secondary emission, and current saturation must be considered. In any case the method should be simple and introduce a minimum of passive material in the final structure.
While all of the above properties are at least partially dependent on the phosphor material employed, they are also dependent on the manner in which the material is deposited. Techniques currently employed involve sedimentation, spraying, brushing, electrophoresis, and photodeposition using various types of polyvinyls. Screens prepared by such techniques are successful in producing numerous commercially available devices, but fall far short of the high resolution and uniformity predicted by the large body of performance data available on such devices. The poor resolution appears to result mainly from the presence of abnormally large particles, agglomenations of small particles, and general variations in the layer thickness.